1. Field of the Invention
The present invention relates in general to an electric fan with a head capable of unidirectionally or opposed-directionally rotating and thereby shifting the direction of the wind in the two modes and, more particularly, to a structural improvement in a wind shifter of such a fan for carrying out either of the unidirectional wind shifting motion and the opposed-directional wind shifting motion using a common output shaft.
2. Description of the Prior Art
In the art, electric fans having two wind shifting modes capable of unidirectionally or opposed-directionally shifting the direction of the wind are known, for example, from Korean U.M. Appln. No. 91-22079 filed by the applicant. It has been noted that a unidirectional wind shifting fan, whose head unidirectionally rotates and thereby unidirectionally shifting the direction of the wind, is preferably used in a large place, such as a workshop, whereinto people crowd. However, such a fan has a problem that the effective airflow of the fan is somewhat reduced and this deteriorates utility of the fan. In an effort to overcome the problem of the typical unidirectional wind shifting fan, the applicant proposed the fan having two wind shifting modes by the above Korean utility model application. In this fan, a mandrel shaft is concentrically sleeved by a sleeve shaft, thus to form a dual output shaft for rotating the head of the fan. The two shafts of the dual output shaft charge the unidirectional wind shifting mode and the opposed-directional wind shifting mode of the fan respectively. That is, when the mandrel shaft of the dual output shaft rotates by the rotating force of a motor, the head of the fan alternately rotates in opposed-directions by a crank and a crank rod, both being provided on the end of the mandrel shaft. In this case, the direction of the wind of the fan is opposed-directionally shifted by the reciprocating rotation of the head. On the contrary, when the rotating force of the motor is applied to the sleeve shaft of the dual output shaft, a revolving pulley fitted over the end of the sleeve shaft unidirectionally revolves round a sun pulley, which pulleys are connected to each other by an endless belt. In this case, the direction of the wind is unidirectionally shifted.
In order to selectively transmit the rotating force of the motor to either of the two shafts of the dual output shaft, the above fan having two wind shifting modes has an output switching device. In Korean U.M. Appln. No. 93-3852, there is proposed an improved clutch for achieving smooth motion for switching the wind shifting mode of the fan between the two modes, that is, the unidirectional mode and the opposed-directional mode.
The typical fan having the two wind shifting modes has a problem that the fan shifts the direction of the wind by means of one of two exterior units provided in the exterior of a housing. That is, when the mandrel shaft of the dual output shaft rotates, the direction of the wind is opposed-directionally shifted by the first unit, comprising the crank and crank rod. On the contrary, when the sleeve shaft of the dual output shaft rotates, the direction of the wind is unidirectionally shifted by the unidirectional revolution of the revolving pulley of the sleeve shaft round the sun pulley connected to the revolving pulley by the belt, which pulleys and belt constitute the second unit. The two exterior units for wind shifting operation enlarge the size of the fan and may cause trouble of the fan, and make fabrication of the fan be difficult. Another problem of the fan is resided in that the opposed-directional revolution angle of the pulley revolving round the sun pulley or the reciprocating rotation angle of the head of the fan is inevitably limited to 180.degree..